What is ONU, ONT, SFU, HGU and the differences between them

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When it comes to user-side equipment in broadband fiber access, we often see terms such as ONU, ONT, SFU, and HGU. What are they? What’s the difference?

1. ONU and ONT

The main application types of broadband optical access include: FTTH, FTTO and FTTB, and the user-side equipment have different forms under different application types. The user-side equipment of FTTH and FTTO is used by a single user, which is called ONT (Optical Network Terminal). The user-side equipment of FTTB is shared by multiple users, called ONU (Optical Network Unit).

The user mentioned here refers to the user independently billed by the operator, not the number of terminals used. For example, the ONT of FTTH is generally shared by multiple terminals in a home, but only one user can be counted.

2. Types of ONTs

ONT is the modem, which is divided into SFU (Single Family Unit), HGU (Home Gateway Unit) and SBU (Single Business Unit).

2.1 SFU

SFU generally has 1 to 4 Ethernet interfaces, 1 to 2 fixed telephone interfaces, and some models also have cable TV interfaces. The SFU does not have the function of home gateway, the terminal connected through the Ethernet port can dial up to the Internet, and the remote management function is weak. The modem used in the early days of FTTH belongs to SFU and is rarely used at present.

SFU

2.2 HGU

The modems equipped by FTTH users opened in recent years are all HGUs. HGU usually comes with wifi and has a USB interface. Compared with SFU, HGU has the following advantages:

  • HGU is a gateway device, which is convenient for home networking; while SFU is a transparent transmission device and does not have gateway capabilities. It generally needs the cooperation of gateway devices such as home routers in home networking.
  • HGU supports routing mode, has NAT function, and is a layer-3 device; while SFU type only supports layer-2 bridge mode, which is equivalent to a layer-2 switch.
  •  HGU can realize its own broadband dial-up application, and the connected computers and mobile terminals can directly access the Internet without dial-up; while SFU must be dial-up by the user’s computer or mobile phone or other terminals, or dial-up through a home router.
  • HGU is easier for large-scale operation and maintenance management.

HGU

2.3 SBU

SBU is mainly used for the access of FTTO users, generally with Ethernet interface, some models have E1 interface, fixed telephone interface, or with wifi function. Compared with SFU and HGU, SBU has better electrical protection performance and higher stability, and is also commonly used in outdoor occasions such as video surveillance.
SBU

3. Types of ONUs

ONU is divided into MDU (Multi-Dwelling Unit) and MTU (Multi-Tenant Unit).

The MDU is mainly used for the access of multiple residential users under the FTTB application type, and generally has at least 4 user-side interfaces, usually 8-way, 16-way, 24-way FE or FE+POTS (fixed telephone) interface.

MDU

The MTU is mainly used for the access of multiple enterprise users or multiple terminals in the same enterprise in the FTTB scenario. In addition to the Ethernet interface and the fixed telephone interface, the MTU may also have an E1 interface. The appearance and function of the MTU are generally the same as those of the MDU, but the electrical protection performance is better and the stability is higher. With the popularity of FTTO, the application scenarios of MTU are getting smaller and smaller.

4. Summary

Broadband optical fiber access mainly adopts PON technology. When the specific form of user-side equipment is not distinguished, the user-side equipment of the PON system can be collectively referred to as ONU.

PON

ONU, ONT, SFU, HGU… These all describe the user-side equipment of broadband access from different perspectives, and the relationship between them is shown in the following figure. Contact us (info@bonelinks.com) if you have any questions.

ONU ONT SFU HGU

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